


Sister Dearest

by Anonymous (orphan_account), Butterfly_Dream, mecchacumming



Category: Love Live! Sunshine!!
Genre: Creampie, Developing Relationship, Dirty Talk, Exhibitionism, F/F, Incest, Reunion Sex, Romance, Secret Relationship, Sibling Incest, Size Kink, Skinny Dipping, Travel, Underage Drinking, as a treat, dia's got a dick, dw about it, my fbi agent is dying inside watching me type these out, ruby can have little a wine
Language: English
Status: Completed
Published: 2020-04-24
Updated: 2020-11-30
Packaged: 2021-03-01 22:54:07
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 19,312
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23824891
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/Anonymous, https://archiveofourown.org/users/Butterfly_Dream/pseuds/Butterfly_Dream, https://archiveofourown.org/users/mecchacumming/pseuds/mecchacumming
Summary: Dia and Ruby have always been close, but during their vacations they find out just how much they need each other.(A series of one-offs set in the same timeline: the first by mecchacumming and an anonymous collaborator, the second by Butterfly_Dream, and the third by meccha.)
Relationships: Kurosawa Dia/Kurosawa Ruby
Comments: 15
Kudos: 96





	1. Sister Dearest

**Author's Note:**

> sup
> 
> this was a collab with someone who chose to not make an account for... obvious reasons. still, thanks to them for writing it with me :) i'm really happy with how our writing meshed, and we had a lot of fun.
> 
> an obligatory disclaimer: incest bad! don't do it! shouldn't really need to spell that one out for anybody, but y'know, here we are. this is a fantasy scenario between consenting adults, emphasis on 'fantasy'. please don't go wearing skimpy clothing for family members.

Flurries of snow fell upon the quiet town of Numazu, sticking to the ground and turning the landscape a pristine white. Bundled up in her favorite black coat, Dia stepped out of her car and headed up the walkway to her family home. A gust of wind swept across the yard, blowing her hair all over her face. Huffing crossly, she brushed it out of her eyes, barely able to keep herself from sprinting to the door in order to get inside. That would be uncouth for someone like her, though. Instead, she paced herself properly, pulling out her keys to unlock the door and step inside. A sigh of relief escaped her lips as she was engulfed in the warmth of the Kurosawa household.

The sound of the door closing shut was ample enough to reverberate through the foyer, all the way to the bedrooms, where Ruby was hard at work studying. Hearing the sound, she stole a sidelong glance at her calendar, just so that her heart wouldn't be crushed if it meant anything other than what she desperately hoped it meant. But there was the date, with the beginning of Dia's winter break circled in pink highlighter and dotted with hearts. Hastily, she marked her spot in her textbook and stepped outside into the hallway, only stopping to smooth the wrinkles in her skirt and run her fingers through her pigtails. She wanted to look her best as she raced forth to wrap her sister in a hug, shouting _"Onee-chan!"_ all the while.

Dia had just finished locking the door when that red blur ran right into her, enveloping her tightly. Letting out a _“pigyi!”_ of surprise, it didn't take long to realize who the culprit was. Honestly, you'd think that she'd be familiar with this happening whenever she came home, but she was still so easily caught off guard.

"Ruby!" Dia shouted. Her surprise quickly melted into a happy smile as she hugged her younger sister back, holding her tight. "I missed you, Ruby. How have you been? Everything going alright at school?"

"It's- it's been going okay," Ruby sputtered out aimlessly. She was much more focused on Dia's warmth, how wonderful it felt to have her sister pressed close against her. Realizing that she should be a good little sister, though, she let go with a quiet whimper of disappointment, if only to help Dia take her coat off. "I'm doing well, but... I miss having you here to help me," she added quietly. Tears pricked at her eyes. "I missed you so much..."

"I missed you too, Ruby."

Dia allowed Ruby to help remove her coat, smiling throughout their ritual. She didn't recognize any of the signs of her sister's disappointment, nor was she looking for any. She was just relieved to be home, and happy to be in familiar surroundings. That didn't mean she was ungrateful: nothing could be further from the truth! Being away from the life she had known while at university made her appreciate those things and those people that much more. That went double for her sister.

"I'm going to go drop my bag off in my room, okay?"

"Oh! Um..." Ruby looked down at the ground, as if the tile were the most interesting thing in the world. She couldn’t bear the thought of Dia being out of her sight for even a second so soon after she’d gotten home, so she said the first thing that popped into her head. "Could I carry it for you?" The words came out as little more than a mutter, but soon Ruby willed herself to look Dia directly in the eyes, the emerald green a reflection of her own. "You must be really tired after your trip, Onee-chan. I want to take care of everything for you, okay?"

"Huh?" Again, Dia was caught off guard. It didn't take long for her to agree, though, smiling warmly at her sister. "Of course. I appreciate it, Ruby. I'll meet you in the kitchen, alright?" Handing her back to Ruby, Dia absconded for the kitchen. Her drive home had made her hungry, and she needed a snack to tide her over until dinner with her family.

Ruby frowned as Dia walked away, leaving her standing alone in the foyer. That wasn’t how her request was supposed to turn out, and all she could do was pout. Maybe it was wrong of her to feel jealous of nothing more than a snack, but she couldn't help herself. It didn’t matter if they were apart for even a second; it was the principle of the matter, not the length of the time. How could Dia leave her alone so soon after returning? Her place was by Dia’s side, after all, hanging off her arm if she could help it.

With a childish huff, she lugged Dia's bag into her room, setting it down and surveying the barren walls. At the very least, she figured, she might as well unpack for Dia while she was here. That in mind, she set about removing everything and hanging it up, blouses and skirts and underwear all neatly folded or hung in the closet. Before initially thinking she’d finished, however, Ruby found one last outfit tucked away at the bottom of the bag almost as if it were meant to be out of sight. With her brows furled, she pulled it out and gasped - it was a sheer blouse and short short combo, the top frilly and pink. Along with it came a translucent bralette that matched the blouse, trimmed with flowery lace, and Ruby found herself blushing at an adventurous side of Dia she never even knew existed.

Suddenly, a thought popped into her head, one entirely unlike her; she should wear it. Surely her sister would be mad, but... Ruby wanted to get Dia’s attention. She didn’t just want to be Dia’s little sister, the kind that could be easily ignored; she wanted to be _seen._ Grasping the bundle of fabrics like they were state secrets, Ruby slipped away to her room to change. Tucked away in the back of her closet, she had one last item that would complete the outfit.

Meanwhile Dia stood in the kitchen, reveling in some pudding as she relaxed and waited for Ruby to return. She was truly an innocent lady, nevermind that less-than-innocent underwear she may or may not have had stashed away. Not that she realized that had been discovered... yet. Her ears perked up at quiet footsteps from behind her, knowing that Ruby had come to join her.

"So, Ruby, how-" She turned around, and the words died in her throat. The spoonful of pudding she held froze in place, her hand halfway towards her mouth. Eyes wide, she stared at Ruby standing there in clothes that she knew all too well.

The warmth flooding her cheeks let her know that she was blushing something fierce. That outfit was too... too hot for Ruby to be wearing. Of course, it had been in Dia’s bag, but... no, that wasn't the point! Had it never occurred to Ruby just how sheer that blouse was? Dia could see her bralette underneath it, hinting at a part of her body that she was never supposed to see. 

"R-Ruby? A-Are you wearing my clothes?" she stammered, sounding stupider than she would have liked.

Ruby giggled and blushed, doing her best to look as innocent as possible. She'd grown up since Dia last lived at home, but even still, she couldn't quite figure out what had come over her as she stood there, moving about so that Dia could take in the sight of the all-too-revealing outfit.

"W- well, I was going to put away your clothes for you," she explained. "But then I saw this, and it looks so cute, Onee-chan! Remember when we used to make idol outfits and model them for each other?" Her voice was saccharine sweet, and she hoped it had an effect on Dia, even after all these years.

Dia swallowed thickly, her eyes drawn to every inch of her younger sister as she twirled around like a little fashionista. Shamefully, so utterly shamefully, the thought crossed her mind that Ruby's butt looked good in those short shorts. It was (likely) inevitable that she would grow into a more feminine woman. That cutesy, childish look of hers was bound to mature with age, and Ruby was eighteen already. It was just that this was her _sister_ that she was talking about. In her mind, Ruby was still the little crybaby in pigtails who’d always trailed after her like a lost puppy. Seeing her sweet, innocent Ruby twirling around with her bra visible was too much for Dia’s poor brain to comprehend.

"Y-Yes, I... I do remember that," she murmured, almost completely dazed by what was happening. Of course, when they’d modeled idol outfits for each other, none of them had been so _risque_. She had never felt anything close to what she was feeling now back then. No more words would come out of her mouth. All she could do was nod stupidly with red splotched on her cheeks as Ruby stepped closer, now just a short distance away from Dia.

Even though she didn't have much to work with, Ruby found herself subtly adjusting her gait so that her breasts were pushed out. She couldn’t quite rationalize the way she was manipulating her body; it just felt _right_ to be doing this, so much so that she couldn’t bring herself to back down. "Do you think this looks cute on me, Onee-chan? I bet it looks even better on you," she concluded with an inflection that just hinted at a tease. "You always were so beautiful in anything."

Now swallowing, even thickly, was near impossible, as Dia's mouth had gone completely dry. Ruby was standing way too close to her, acting so... so provocative. There was no other word that could describe it. The way she was acting was something Dia expected from _Mari_ , not from her innocent sister.

"Well, what... what do you expect?" she muttered, wishing that she didn't appear as out of sorts as she knew she did. "I always rock such outfits." Her normal confidence sounded forced with the way her voice shook. For goodness’ sake, she couldn't stop staring at her sister's breasts! They weren't anything special, but then again, puberty hadn't been kind to her either - neither of them were destined to compare with their friends, at any rate. "But, yes, you... you look very cute in that outfit. Sexy, even." Wait, what? Had she just said Ruby looked sexy in her outfit? What was wrong with her?!

As Dia fretted about the words she had just spoken, Ruby was turning them over in her mind. She knew that they weren’t okay, but… she had never been told that before. She had never thought of herself as _sexy_ , but coming from the person whose view mattered to her more than anyone else’s, the word only made her heart beat faster as her body began to act with a mind of its own. A giggle flittered about in the air as Ruby stepped just ever so slightly closer, just to see how far inside Dia's personal space she could get.

"You really think I'm sexy?~" she crooned. "It's been a really long time since you've been home, Onee-chan. I grew up a lot. And, well... so did you. I want to catch up with my Onee-chan, and find out what she was doing in these kinds of outfits." A hand coyly snaked its way into Dia's, threading their fingers together as she looked up with bright, innocent eyes.

Dia paled noticeably, her hand unconsciously squeezing Ruby's. "I..." What had happened to her confidence? She had never felt this speechless around her sister before. If Ruby had really matured so much, did that mean she was gaining an advantage that she hadn’t had before?

"I would never do whatever you might be implying," Dia finally responded, but it sounded weak. How could Ruby look so innocent when what she was saying was anything but?

"Oh," Ruby replied, lacing dejection into the sound. "I hoped you had some fun stories to tell. Maybe... we could make some?"

Ruby looked down, and felt her breath hitch when she saw a bulge forming in Dia's pants. She couldn't grasp exactly what she was doing, not when a flurry of emotions was clouding her brain and fogging her judgement. She had missed Dia so much, and the thought that her precious Onee-chan would ignore her for even a single second was so abhorrent as to morph that longing into something possessive and much less platonic.

Now, seeing the evidence of Dia’s arousal, Ruby’s feelings were only amplified as her thoughts drifted to Dia's college life. Had Dia been doing anything? Was there... a boyfriend? A girlfriend? The thought made Ruby’s eyes well up. Onee-chan was _hers_ , and she didn't want anyone to take Dia away.

"Mom and Dad aren't home," she whispered, letting the implications linger in the air uneasily.

"They... aren't?" Die asked in reply. Was it hot in the kitchen all of a sudden? Someone needed to turn the thermostat down. Maybe she needed to. She looked down at Ruby, whose expression carried so many emotions that Dia wasn't sure which one to focus on. None of them could distract from her erection, though, and her face started heating up as she tried to subtly adjust herself. "Ruby, just... just what exactly are you implying?" She ran her tongue across her lips, trying to get some moisture going. Why was she getting hard in front of her little sister? This wasn't right! ... Why did that make her harder?

"Nothing," Ruby replied sweetly. "Just... your trip must have been long, and you just got home. I bet you're so stressed, Onee-chan. I just want to spend some time with you and help you relax."

"It... was a long trip," Dia murmured, unable to disagree with that sentiment. It was always nice to have some way to relax after a long drive, even if that wasn’t going how she’d intended it to.

In response to the sentiment, Ruby let go of Dia's hand, but instead of letting them entirely part she chose to grab Dia's wrist instead, leading her hand to the top Ruby was wearing. She guided it all across the fabric, letting Dia's hand roam her barely-covered skin, inching closer and closer to her breasts, to the point of no return that she found herself skirting so brazenly.

"What did you buy this top for, Onee-chan? Were you trying to make someone notice you?" She looked up with innocent eyes, waiting to see what Dia would say.

Dia sucked in a breath when she saw her fingers were going, where Ruby was guiding them. "N-No, of course not!" She did her usual deal of denying things, her face turning red as she actually let the truth out. "I... I wanted to feel sexy."

"You've always been sexy to me," Ruby replied softly, so soft that some part of her hoped it could be passed off as a stray noise. She meant it, though, and her confession was out in the open now. "Everything about you just... makes me feel so weak..." Taking the plunge, she finally pulled Dia's hand to one of her breasts. All that separated her older sister from her breast was just two thin, sheer strips of fabric. It was so wrong, but all she knew was that she wanted this, to be _Dia’s._

"D- do you want this, Onee-chan? Do you want me?"

"Ruby..." Dia made a noise somewhere between a gasp and a whimper. She could scarcely believe where her hand was, but she made no attempt to remove it. For several moments, they both stood there silently, Dia's hand on Ruby's breast and her sister's request hanging in the air. Dia was sure her heart was about to beat right out of her chest. Then, before her brain could react properly, she wrapped her arm around Ruby's back and pulled her close. As soon as their bodies were pressed against each other, she kissed her. She was kissing her little sister, she was groping her little sister's breasts, and she wasn't even trying to stop herself.

"Look what you've done to me," she panted against Ruby's lips, getting her words out in between their stopgap kisses. "This is wrong, Ruby, and I can't stop myself..." As if it were Ruby's fault that she had given in to this unholy desire.

As soon as their lips connected, Ruby melted into Dia, taking the chance to finally wrap her arms around her sister's body, to get as close as possible. As her small breasts were felt up and harshly groped, she moaned shamelessly for Dia to hear. Her Onee-chan was home, finally, and they were together - now Ruby could show just how much Dia meant to her. As soon as their lips broke off for a split second to catch some breath, Ruby finally spoke.

"Onee-chan, I'm so wet," she mewled. "I want you so badly...." A hand reached between them, slowly venturing lower and lower until finally her fingertips fulfilled a promise, brushing up against the bulge in Dia’s pants.

They had already crossed the threshold, but now it had been thoroughly smashed, and it sent Dia reeling. Though she had gone on the offensive, her body had done so without her consent. Now it froze up as Ruby's hand made its presence known, rubbing on Dia’s erection. She started to blush, knowing that Ruby was getting to feel just how hard she was. Her _little sister_ knew that she was hard for her. It was mortifying, yet strangely gratifying.

"Let me... Let me feel how wet you are," Dia whispered, taking in every inch of Ruby that she could. "Show me how badly you want me." She couldn't believe she was speaking so forcefully, but it felt strangely natural, like she was meant to talk like that.

The way Dia's voice took on its authoritative tone only made Ruby's heat worse, and she was afraid she'd soak Dia's short shorts straight through. Wordlessly, she took a small step back, fiddling with the button and zipper until they were both undone, and guided Dia's hand shakily into her shorts, letting her feel the soaking wet lace underneath. As soon as Dia's hand passed over her clit, she whimpered, her face scrunched up.

"I- I-" she tried to say as she tripped over her words, the lust clouding her mind. "I love when you talk like that, Onee-chan..."

Upon hearing those words, Dia’s heart felt like it was both beating way too fast, yet also not beating at all. She couldn't believe how wet Ruby was: she was soaked! Was this all because of her? She passed over Ruby's clit, feeling the scintillating fabric of lace beneath her skin as her hand moved.

"When did you get this underwear, Ruby?" She was surprised: she had never imagined Ruby to wear something so scandalous. Things really _had_ changed while she was gone.

"I- mmn," Ruby moaned, her whimpers becoming increasingly brazen as Dia massaged her labia slowly. "I... asked Kanan to help me pick them out." Ruby hooked her thumbs on the waistband of her shorts and tugged downward, letting them crumple limply to the floor to reveal the pink lace of the thong, which rode up her hips and left little to the imagination about what lay underneath. "When I tried them on the first time, I was scared, but she encouraged me. She told me that I deserved to look sexy. Do they make you want to do things to me?"

Dia really wanted to let out several choice swears, but her restraint held her back, if only in this one case. Even as she soaked in Ruby’s body, it still felt wrong to be cursing in front of her, cognitive dissonance be damned.

"They... they do," she whispered, though her throbbing erection told more than her words ever could. She couldn't stop staring at Ruby in that tiny pink thong, and the sight left her so hard that it hurt. "I don't know whether to thank Kanan or kill her for this."

Ruby giggled, and she stood up on her toes to kiss Dia once again, taking longer to savor the feeling of those soft lips brushing up against her own. "You can always thank me instead," she crooned in little more than a whisper. "What do you want to do with me, Onee-chan? We have to make up for lost time, after all."

"Thank you..." Dia kissed her back, sighing against her lips. "If we have time to make up, then we should do it in my bedroom." She pulled herself away from Ruby, taking her hand and leading her towards the bedroom, the shorts left to lie on the kitchen floor.

Ruby’s heart nearly thumped straight out of her chest as she was led along, Dia’s grip on Ruby's hand firm enough to send wonderful shivers through her body. With Dia taking a more assured role, Ruby found some of that alien confidence melting away now that it was no longer needed.

"Um... Onee-chan? Could you... have me on my bed? I'd really like that..."

"Your bed?" Dia stopped, pondering the thought for a moment. Then she nodded, changing course to lead them to Ruby's bedroom. "Yes, come on then." Confidence wasn't foreign to her, but what they were doing was. She wasn't an assertive bedroom presence, and certainly not with her damn sister. Ruby being a teasing little minx worthy of Mari had triggered some sort of response inside her, though. She wanted to do this now. Her hard, throbbing erection was guiding her now, not her brain.

They stepped inside, and as Dia shut the door gently behind them, Ruby moved to the bed and swept a few stray plushies off of it. She wasn't sure what possessed her to suggest this, but there was something about being taken in her own bedroom, among all the evidence of an innocence she'd been so quick to discard, that was wonderful to her addled mind.

Even Dia felt a sense of hesitance as she saw all the normal fodder that made up her sister's room. Everything was still as pretty and pink as it had been for years, giving rise to a churning of guilt in her stomach. Was she really about to defile her sister's innocence in her childhood bedroom? She approached Ruby, who moved her hands to Dia's pants.

"It must hurt, Onee-chan. I'm going to take it out now, okay?"

Even with the doubts waging war in her mind, it was hard to feel anything but the arousal that had been blooming within her when Ruby spoke.

"It does hurt," Dia muttered, taking a deep breath as horny confidence overtook her. "It hurts, and it's your fault for making me feel this way. Please take care of it right away."

Ruby's breath hitched as the words left Dia's mouth, and she hastily fumbled with Dia's fly until it finally fell undone, allowing her to pull it down and bear witness to Dia's erection, tenting the fabric of her panties. Even the veins of her cock were on full display, so tight was the fit, and Ruby was nearly drooling as she looked down at it. It was Dia's cock, her _big sister's_ cock, and it was hard because of what Ruby had done. Absentmindedly, her thighs rubbed together, anything to relieve the ache in her core as she imagined it filling her up.

"I'm so sorry, Onee-chan," she replied dutifully. "I'll- I'll make it all better, like a good sister should." Without even thinking, she dropped down to her knees on the carpet, freeing Dia's cock from its constraints and placing a gentle, delicate kiss on its tip. Before she could focus on her own arousal, she had to make Dia feel better. That was what mattered.

A small moan escaped Dia’s throat, her cock still throbbing painfully. The sight was hard to fathom as she watched from above, breath weak and shaky. Ruby was down on her knees, doting on her cock because she had told her too. How could she have done that? But... it felt too good to really worry about that. She needed relief, no matter what - or who - gave it to her. It was perfectly alright if Ruby was the one to do it. No, it was _better_ if it was her.

Suddenly Dia found herself insecure, however. "I'm sorry for... for how I must appear," she murmured, a light blush crossing her face as she stared down at her own cock. An above-average eight inches, it throbbed like mad in front of Ruby's lips. "I know it's not very... very sexy..." The truth was in the clothes Ruby was wearing, the ones Dia had bought in a sudden rash of confidence one day; she’d wanted to feel sexy. Now, though, the way her cock was too big to even fit in her panties made her feel unattractive.

Ruby's answer was the way her lips parted, though, the way they took the head of Dia's cock between them. Her hands reached for its base to slowly stroke its substantial length, moving back and forth in soothing motions as another hand idly played with Dia's balls. She had never watched much porn, always scared of what Dia would think - a thought that now seemed only ironic - but somehow it all came to her so naturally. She was a good sister, and taking care of her Onee-chan was in her nature.

When her lips left Dia, a silvery strand of saliva connecting them, she looked up with warmth in her eyes. "You look so incredible, Onee-chan. You turn me on so much," she replied, her hand still stroking Dia's length. "You're so beautiful and feminine, but... I think I love your cock most of all." She returned her lips to it, slowly working herself farther and farther down Dia's shaft.

"You... you do?"

Dia couldn't keep the moans inside anymore, not as Ruby took her cock like that. Throbbing within the safety of her sister's warm mouth, she felt her body begin to shake. It wasn't much, but it was noticeable, especially once Ruby began to fondle her balls. They were the most sensitive part of her body, and Ruby was getting to experience that firsthand. Dia blushed, her face heated with more than just embarrassment as she watched her little sister take more and more of her cock.

She had no clue where Ruby had learned how to do something like that, but as Ruby's movements gained more and more confidence, she found herself unable to worry or even to hide the truth: she was turned on, and Ruby was the one turning her on. She had her cock out and shoved down her sister's throat, and she liked it being there.

Dia's cock slid further and further back in Ruby’s throat, and soon Ruby could taste Dia's precum leaking out, the salty taste serving as encouragement for her to be more enthusiastic. She looked up at Dia, eyes wide and demure as she continued servicing her sister. She wanted nothing in the world more than for Dia to feel good, and the blush on Dia's face was proof enough to fill her with a sisterly kind of pride. A hand even snaked down to her panties, pulling them aside to slide two fingers inside, gathering her slick and bringing it to Dia's cock to use as a lube as she stroked Dia's shaft more.

Now, Dia couldn’t help but feel that this was starting to feel _too_ good. She had a sudden worry that she was going to bust too quickly, and there was supposedly a lot of time for them to make up.

"Stop," she commanded, grabbing Ruby's pigtails and tugging upwards on them. "Let's... let's not get too carried away. I want to..." She felt her face heating up again. What she wanted to say was so embarrassing, and wrong, and... and so fucking hot. "I want to fuck you, Ruby. I want to fuck your wet pussy, because I'm the one who made it wet." With Ruby's lips off her cock, she stepped back and started to undo the buttons on her blouse. "Take off your clothes for me."

The act of having her pigtails pulled like that was enough to ruin the last ounce of Ruby's patience to have Dia inside of her, so the order came as a blissful reprieve, though some strange pang of disappointment nagged at her now that she wasn’t sucking Dia’s cock.

"Y- yes, Onee-chan. You made my pussy wet." Obediently, she slid off her panties, a process made all the more difficult by how wet they were and how tightly they fit on her body. The fabric clung to her skin until finally it was off, tossed aside onto the floor with a quiet _plop_. Next came the blouse, which she tugged off just as Dia was finished unbuttoning and removing her own top. Ruby took a moment to stare lovingly at Dia's body, admiring the elegant bra she had on, before removing Dia's bralette from her own body.

Now that Ruby stood there, naked, vulnerable, and ready to be taken, it took every ounce of Dia's self-control to not jump her right then and there. Her hands were shaking as she unhooked her bra from behind and let it fall from her body. Finally the two sisters stood naked together, in a room so full of innocence. Ruby’s plushies didn't need to see what Dia was about to do to their owner, and even Ruby couldn’t help but mouth a silent _‘I’m sorry’_ to Mr. Fluffikins, who stood watch over her sanctity from the corner of the nightstand.

Still, none of that was about to stop them, not now. In a flash, Dia crossed the small distance she had put between them, latching onto her sister and kissing her with every ounce of strength she had. Her hands explored every inch of Ruby's body, eliciting quiet gasps with every touch and sudden movement. They had taken baths together, but it had never been like this. It had never felt inappropriate, or hot. Her cock throbbed up and down, smacking against Ruby's quivering, tiny thigh, seemingly big enough that it might tear up her poor little pussy. At that point, though, Dia couldn’t even care. Ruby had made her horny, and Ruby was going to take care of her.

To prove the point, Dia reached for Ruby’s ass and palmed it harshly, prompting Ruby to squeak and melt further into the kiss. She parted her lips as if purely by instinct, allowing Dia's tongue to slip between them. The feeling of Dia’s cock was too much for her, and the heat that it radiated only served to make her more and more desperate for her sister's touch.

"Onee-chan... please fuck me,” she begged into Dia's lips. "Please fuck Ruby's slutty pussy. Make me apologize for doing this to you, I can't take it anymore..."

Instead of answering, Dia just growled: an animalistic sound that bored deep into Ruby's ears. Reluctant as she was to stop grabbing Ruby's ass, she did so in order to push her sister onto the bed. Lording over Ruby with her cock pointed right at her sister, she continued her commands.

"Lay on your back, Ruby. Spread your legs and let me see your cunt." She was too far gone now to think about what she was saying. Even though it was uncharacteristically harsh, enough to leave Ruby weak and trembling, it was just what felt right. All Dia knew was that she was going to do what felt right: in this case, Ruby.

And in turn, Ruby basked in Dia’s unwavering attention, something that she craved even more now that it was so unquestioningly _dominant_. Without even thinking of disobeying Dia’s command, she leaned backwards and splayed herself across the bed, spreading her legs wide so that her sister had a full view of her pussy and the stained sheets beneath it.

Dia walked to the edge of the bed, staring between Ruby's legs and licking her lips. Now, Ruby’s brazen arousal was on full display, and a rush of emotions surged in Dia’s brain. It was such a slutty thing to do, staining the bed like that. Her sister was _slutty_. Narrowing her eyes, she hoisted herself onto the mattress, her cock throbbing between her legs and bouncing against her thighs as she crawled to her sister.

"Hanging around Kanan has been bad for you," she snarled, suddenly pouncing Ruby. Her palms pressed flat against the sheets, boxing Ruby's head in between them. Her eyes bored down into Ruby’s, showing that there was no nice, doting older sister there anymore. She was horny, and she was mad. "You've become such a slut. Just look at yourself." She dragged her cock along Ruby's wet slit, letting it flick a couple beads of juices down her stomach. "I'm going to have to show you how I feel about sluts."

Ruby whimpered and mewled, so scared and so aroused by the dominant energy that had possessed her sister. She grinded shamelessly against Dia's thick cock, not even considering that she was only confirming Dia's views - all she could think of was Dia inside of her.

"I'm- I'm so sorry, Onee-chan," she cried out pathetically. Tears pricked at her eyes, both from the shame and the arousal, but she never stopped grinding, never stopped desperately praying that Dia would up and take her. She was like a madwoman, possessed by how beautiful her sister looked when she was angry. "I let you down... please punish me for being a bad, slutty little sister, Onee-chan. Please use your cock to make me into a good girl again!"

There was a moment's hesitation on Dia's part, seeing the tears forming in Ruby's eyes. Then she felt the grinding against her cock, and the words coming out of her sister's mouth. Narrowing her eyes further, Dia got on her knees to keep herself balanced, then plunged her cock inside Ruby. There was no gentleness to her actions, or other foreplay to make her ready. Not that Ruby needed to be, however. Dia’s girth was hard to take, but Ruby had become so wet and aroused that it only felt natural to be stretched wide open the way she had been.

Dia's cock moved with ease, and the pain quickly turned into an indescribable pleasure and heat that moved throughout Ruby’s whole body. Her sister was home, and they were together again. She had no need to be jealous when Dia was here, in her room, breeding Ruby like there was no tomorrow.

"Onee-chan!" Ruby cried out. "Fuck me, Onee-chan! I need you to make me a good girl!" She wrapped her arms around Dia's neck, and brought them together for a long, slow kiss.

Dia kissed her back in turn, allowing herself to be drawn down against her sister's needy lips. Dia felt a strong need burning deep inside her core as well, one that she had never acknowledged before. She hadn’t even known it existed, but it was there all the same. It was obvious just what the truth was: she liked fucking her sister; taking control of her. Ruby was so easy and willing, just lying there naked and allowing herself to be taken without any resistance. 

Eyes closed, Dia kissed Ruby with fervent passion, letting out the occasional pant or growl as she slammed her hips down repeatedly. She would lift herself up, then down again, quickly speeding the pace up as she fucked her little sister down into the bedsheets. No longer would Ruby be without someone to show her how to behave - come hell or high water, Dia would make Ruby into the best girl she could be.

With her missive in mind, Dia's movements grew almost animalistic in their urgency. Ruby mewled and whimpered as Dia's cock impaled her over and over, and eventually those small sounds grew and grew into a chorus of moans as she cried out for her sister. Dia was right: Ruby had become a slut, and it was apparent with every plea for more that escaped her lips. Her legs wrapped themselves around Dia, holding her tight. At least she was here now to make everything better - Ruby loved her sister dearly for that, and she didn't try to hide it. Her love was the way she pressed her lips tightly against Dia's, how she withstood Dia’s passion. Dia's attention was hers, and she wouldn't give it up for anything.

In the haze of lust that had settled around their sisterly union, Dia began to do things she should have known better than to do. She forcibly removed her lips from Ruby's, instead pressing them against her neck. She bit down and licked the supple skin, leaving hickies and bite marks all over. Ruby gasped as she felt Dia's mouth on her neck, and the pain caused tears to well up.

The marks would be hard to hide, but Dia wasn't in any right state of mind to linger on that. It was hard to be smart when her instincts told her to let her cock do the thinking. Even some small part of Ruby found itself wanting everyone to see the blemishes, to know what had happened - their parents, their friends, their old fans. She wanted them all to know how much of a slut she was for her sister's cock.

Dia refused to let out, her heart racing and breathing ragged as she kept going without slowing down. Her body wasn't in the peak of physical condition, but she wasn't going to stop fucking Ruby. Dia was going to pound her into the bed until a permanent imprint was left in her formerly-innocent, soiled sheets.

Without thinking, Ruby’s hands gripped Dia's backside, nails digging paths into Dia's pristine, supple skin. It seemed only right to show Dia her feelings, but unlike Dia, she was too weak to speak or even to grind back, not when she was being fucked so mercilessly. All she could do was whisper "I love you, Onee-chan" as she tried not to let her eyes linger on the stuffed animals and idol posters all around them.

Dia was too far gone for even that, having lost the ability to see straight. She was staring straight into Ruby's eyes, able to see her little sister bucking and crying beneath her. She saw Ruby’s tiny body bouncing beneath her, but she also was staring right through it. In that moment, it was all about the feeling: the feeling of Ruby's skin beneath her hands and tongue, how tight Ruby’s pussy was wrapped around her cock. The sounds she let out of her throat were animalistic, certainly not human. This wasn't the normal, strict Dia that everybody knew. This was a different Dia: one that only Ruby had now seen. In return, Dia saw Ruby in a new light as well: as a young woman, with needs that could only be described as slutty. That Ruby was slutty for _her_ was very nearly overwhelming.

By now it was hard to take any more, and the devotion they shared for one another was reaching a fever pitch. The creature that had possessed Dia was driving Ruby wild, filling her little head with ideas that she was being breeded and claimed. After all, she knew she was supposed to be a good girl for Dia. Good girls let their sisters do whatever they want to, didn’t they?

Between moans and cries, Ruby finally spoke. "I'm- I'm on birth control," she said. "You can finish inside me, Onee-chan."

Dia didn't respond, at least not like the prim, proper sister she usually was. The best she could offer now was a low growl. Those words had been like a shot between the eyes, making her realize that she really was going to cum inside Ruby, whether or not she was on the pill. In fact, it barely crossed her mind then that she wasn't wearing a condom. She'd gotten so into it that she hadn't even thought to wear one. She hadn't come home expecting to bareback her sister, yet alone anything close, but there they were. She wanted to question Ruby’s use of birth control, but after a few more thrusts, that concern was the furthest thing from her mind.

All the lights seemed to be blinking as Dia came, her body tensing up to the point where she wasn't even thrusting anymore. Her body pressed down on Ruby's, pinning her to the bed and giving her no means of escape. Not that Dia was very strong, but Ruby was even weaker than her sister. Her cock was as far inside Ruby as it could go as she emptied her balls inside her little sister's waiting, willing cunt. Even if it was wrong, it was heaven, and that was all that mattered to either of them. Dia didn't even think about pulling out, not now.

Ruby looked Dia in the eyes as she felt warmth pool up in her womb, trying to convey the love she felt. She was being bred full of Dia’s cum, and it made her happy. With Dia bearing down on her, their breasts pressed flush and her thick cock pulsating inside Ruby, all she could do was lie there and take it all. As Dia emptied into her, Ruby peppered kisses all over - Dia's lips, her face, her neck. Anywhere that she could show her devotion, she eagerly did so.

Only when she felt Dia finish did they untangle themselves, Ruby’s hands and legs falling to the bed in a fit of exhaustion. Dia remained tense for longer after finishing, but gave in as well. Pressed against Ruby's body, she didn't have anywhere to fall when she finally unwound. Her arms and legs flopped against the bed, her head lolling on Ruby's shoulder. Her breathing was heavy, as if she'd had to go through one of Kanan's early morning tortures disguised as an exercise routine. The room was silent except for their gasps for breath and the quiet hum of the heater, and Ruby was content to stare lovingly at her sister.

With their chests pressed together, Ruby could feel Dia’s heart hammering against her ribcage. It all felt so good, even though it was wrong. As full of denial as Dia tended to be, even she knew better than to say that what they had done was anything less than utterly euphoric. So she chose to remain silent, struggling to catch her breath from her incredible exertion.

Ruby was the one who finally summoned the energy to wrap her arms around Dia, hugging her sister tight. "Did you like that, Onee-chan?"

For the moment, Dia just nodded, not trusting her voice to speak the truth properly. She slowly pulled out of Ruby, whimpering quietly at her sensitive, flaccid cock dragging against Ruby's walls. Ruby, too, couldn't help but whimper at the sensation, still sensitive from the number that had been done on her.

"I really loved it," Ruby added under her breath. "I love what you do to me."

With a grunt, Dia pushed herself across Ruby's body, flopping down on her back next to her sister. It was a tight squeeze on a bed that was really made for one person. They were still very close together: their arms pressing against each other, one of Dia's legs slung over Ruby's. Their bodies were heated and coated with sweat, and Dia wished she could turn a fan on.

"Yes," she finally managed to pant out, staring at the ceiling. "You did a wonderful job, Ruby. I..." She was coming down from that incredible high, which meant there was room for guilt and unease to fill in the empty spaces. Still, she had enough of that lust left to say what was undeniably true. "I love doing those things to you."

Ruby smiled softly, and as she turned onto her side to face Dia, a thumb brushed Dia's cheek softly. She knew she should go clean up, but she couldn't bear to part from her sister's side. Dia blushed slightly at such a gentle touch. It felt romantic, as opposed to the voracious sexual appetite the two of them had mere moments ago.

"I- I'm glad you don't regret it," Ruby whispered. Her smile melted into an expression that wasn't quite sad, but unsure. "I know it's selfish, but... I want to have you all to myself. Like when we were younger. When I saw that you wanted me, it made me so happy. I... know that makes me bad."

Dia quickly started to frown when she saw that unsure expression on Ruby's face. "Don't say that, Ruby." Despite her exhaustion, her tone still came out more strictly than she had meant it to. "You shouldn't feel selfish. I let it happen, so..." She sighed, pressing her forehead against Ruby's. "I liked it, Ruby. I really did. I didn't expect it to happen, but... when it was, I couldn't stop. I wanted to... mark you as my territory." She blushed deeper at such words coming from her mouth.

Ruby couldn't help but feel her heart flutter at the weight with which Dia spoke. It was a quick motion to lock her lips with Dia's yet again, and she allowed her hands to roam Dia's body without their feverish pace from before.

Dia sighed and closed her eyes, feeling a sense of peace washing over her as they kissed and touched each other again. It didn't feel like they had done anything wrong, not when everything felt calming. She didn't feel like getting up: not to clean up, get dressed, unpack... anything. All she wanted to do was lie there in bed with Ruby, whose hands felt so soft against her skin.

Dia sighed and moaned when her sister's fingers brushed across her breasts, letting out a noise of surprise when they were grabbed gently before Ruby’s hands glided elsewhere. That was the kind of boldness she still had trouble believing came from Ruby. 

Touches could only speak so much, though, and Ruby let the kiss linger before pulling away slightly, just enough to speak. "It's so sexy when you make me yours," she spoke, and for effect she brought Dia's hand to her neck to rub the patchwork of bruises, their colors staining Ruby's pristine skin. "I can't get enough of it."

"You can't, huh?" Dia blushed when she opened her eyes and saw the blemishes. She had really done a number on her sister, and she hadn't even been thinking when she did it. There was going to be a lot of explaining to do should those be discovered. "You might want to cover those up before our parents get home, though." Not that either of them were interested in getting out of bed and doing the work.

"Mmn," Ruby wordlessly concurred. Some twisted part of her wanted to be caught off guard by their arrival and not be able to cover them up, but this had to come to an end... for the time being, at least. "You're probably right. Can we just stay here a little bit longer? I just got my sister back, so it's only fair," she added with a hint of playfulness. She put on her best puppy dog eyes as she looked at Dia. Even if she needed to clean up, it was hard to pull herself away from her sister's embrace, and she knew how hard it would be to keep to herself once their parents were home. Right now, though, she could do whatever she wanted, safe from prying eyes.

"Yes," Dia murmured, feeling a similar way to Ruby. She knew it was best to be ready well in advance of their parents' return, but she didn't have the strength to get up. Ruby's warmth was overbearing, yet it was lulling her into a sense of deep calm. They were still alone, and that wouldn't change for a bit longer. Perhaps it would be alright to just relax, just for the moment.


	2. Pure Devotion

**Notes for the Chapter:**

> hey again!
> 
> this was originally intended to be a one-off fic, but imagine my surprise when the one and only [Butterfly_Dream](https://archiveofourown.org/users/Butterfly_Dream) approached me with a second chapter already written! after reading this i can safely say i'm a pretty big fan of how he riffed on our fic, and i think y'all will feel the same way. ;) so naturally, i couldn't resist the top ten anime crossovers moment. thanks to him for writing this!
> 
> "y'all knew what you were getting into when you clicked on this. if you didn't, here it is: dia and ruby have smoking hot sex for 4k words. that's it. also thanks for having me featured on this nice little setup :') i'm glad i could contribute to this iconic fic in some way" - Butterfly_Dream

_“Onee-chan…”_

The familiar phrase, whispered sweetly, stirred Dia from her sleep. Not fully awake yet, she screwed her eyes shut, searching aimlessly for a more comfortable sleeping position.

_“Onee-chan.”_

Dia sighed, murmuring something indecipherable in response.

_“Onee-chan~!”_

_That_ didn’t sound normal at all, and it was enough to wake Dia completely. She gasped. Her eyes shot open, but instead of seeing her sister staring down at her as she’d expected, she was only met with the homely wooden roof of the Kurosawa household.

“A dream…?”

A few moments passed before Dia realized she was breathing heavily. Already, the concrete details of her dream were slipping away from her, blurring and fuzzing in her mind’s eye the harder she focused. Ruby’s voice was the lone remnant, high-pitched and satiated as ever.

_Satiated…_

On this particular morning, the oppressive haze of sleep took its sweet time in clearing from Dia’s mind. Her senses returned to her one at a time; her aching thighs, her core, and her mouth were all sore. With each subsequent realization came the increasing feeling that something was off, a feeling that was only exacerbated by the feeling of her bare skin against the bedsheets - not to mention the indeterminable feeling that she wasn’t alone.

There was another presence in her bed.

Dia sat up abruptly. What she saw nearly sent her into shock; there was Ruby, on her hands and knees, face-down and bare naked, her glistening slit bared for Dia to see.

Dia’s face heated up in record time, and the warmth spread throughout the rest of her body. The perversion of this sight, seeing her little sister lying in wait for her without a word, caused every single memory and sensation they had shared yesterday to wash over her like a tidal wave. It banished beyond any shadow of a doubt that they could put yesterday behind them.

The seductive lingerie. Dia pouncing on Ruby. Hurried, whispered declarations of love during their coupling. Reaching her climax as she stared Ruby right in the eyes, seeing their shared desire reflected there. Laying in the afterglow together, any feelings of shame and regret seemingly ways away. All of this came to Dia as she gawked at Ruby, who lay perfectly still and silent. There was no way to misinterpret this.

Not that Dia wanted to forget about yesterday. But that nagging rational part of her mind was still wondering if they should stop. If she didn’t want to think of the consequences now, when would she?

Dia’s own body drew her out of her stupor. At some point, the blood had rushed from her brain to her cock, all eight inches of it standing up. This wasn’t an average case of morning wood - it was her body begging her to take what Ruby was offering.

Without a word or even a turn to look, Ruby reached back and spread her lower lips, two fingers on each side. Her pussy was completely soaked, and the sight only turned Dia on even more. As though she was aware of the animalistic desires stirring inside of Dia, as though they didn’t need words to communicate the fact that Ruby wanted to feel her sister spreading her apart and filling her up like no one else could.

Ruby wiggled her hips, and the last shred of reason fell away from Dia’s mind. She still wasn’t sure where Ruby had picked up on her teasing ways, but her overprotectiveness fell to the wayside as her lust for her sister shot through the roof. Seeing Ruby’s silent invitation, there was little she could do to dissuade herself..

Dia got to her knees and crawled to where her sister waited. Her shoulders were already heaving, and her hands shook with equal parts anticipation and trepidation. She guided her cock to kiss Ruby’s labia, and there she let it rest, rubbing her cock up and down the entrance and feeling Ruby’s arousal coating her cock head.

Ruby quivered beneath her, but kept her face firmly entrenched in the sea of bedsheets. She already had her hair up in its signature pigtails, equal parts cute and now alluring to Dia. Looking at her now, the hickeys and bruises she’d left yesterday were more than visible. They’d covered them up yesterday with a well-placed scarf, and Dia figured they’d need a bit of foundation on top of that if they wanted to keep the proof of their love hidden.

That was something to worry about later, though. For now, Dia gripped Ruby’s hips, not intending on letting go until she’d emptied herself inside. With one last look at Ruby’s waiting, prone body, she drove her entire cock inside, spreading apart the walls of Ruby’s pussy with lust-driven force.

They moaned as one, though the sound for Dia was more like a grunt. Ruby pushed her face deeper into the bedsheets, her whole body shaking from the power of Dia’s singular thrust. The mere thought of having her sister’s bare cock inside of her made her soaking wet, all the more so now that it was actually happening. She wanted Dia to use her as she saw fit, to fuck her until they were both sore and sweaty.

Dia desired the same thing out of Ruby. There was plenty of time for slow, sweet lovemaking later, when they’d fucked all of this pent-up lust and desire out of each other. For now, Dia leveraged Ruby’s hips even harder, rocking them back and forth in time with her thrusts as she relentlessly pounded Ruby’s pussy. Ruby clutched at the bedsheets, feeling how deeply and completely Dia penetrated her. It still hurt to be spread apart this far, but even that didn’t compare to the arousal that yawned in her very core. That was a place that only Dia could reach with her impressive cock, railing her like they were the only two people in the world.

Since their parents were home, Ruby knew better than to sigh and shout for Dia at every opportunity. She didn’t need to beg, anyway - Dia knew exactly how to slake her thirst. But her muffled moans and Dia’s grunts allowed room for a new, perhaps lewder sound to take its place: that of Dia’s hips slapping Ruby’s ass every time she bottomed out. Another sound contributed to this dirty cacophony: the quieter yet equally lewd slicks, Ruby’s natural lubricant working overtime to aid Dia in fucking her.

If anyone were listening, it would be painfully obvious that they were fucking. That primal lust from yesterday had long since overtaken Dia, allowing her to keep up her frantic pace even as her body complained and her sore limbs ached. Ruby’s teasing tactics had worked like a charm, and now Dia was going to fuck her as hard as possible in return.

Dia knew she couldn’t last too long; Ruby just felt _that_ good. She didn’t mind being a quick shot, especially If it minimized the risk of anyone hearing, and she knew Ruby didn’t mind either. They desired the same outcome. With a familiar pressure building in her cock, Ruby’s inner folds aiding and extracting every bit of pleasure from her, they didn’t have to wait long for it. There wasn’t much that could stop Dia at this point.

Unfortunately, Dia was present enough to perk up at the one sound that could: footsteps down the hall. Addled by lust as she was, though, she was _not_ sensible enough to stop railing her sister, merely slowing down to listen a bit closer. Ruby wasn’t helping on her end, even pushing her hips back in time with Dia’s thrust, ensuring she buried her entire cock inside each time.

But the footsteps glided across the wooden floor, far too close for comfort. Far too close for them to continue their union in secret, actually. Dia was forced to spare a glance towards the door. As she watched, dismayed and still extremely turned on, the shadow of a figure peeked out from underneath the door - right when the footsteps stopped.

“Dia?” Their mother’s voice sounded from right outside the door.

Dia stopped cold, but not before her hips met Ruby’s ass one last time. The smack was much louder than she wanted it to be. Dread crept into her limbs. With the utmost caution, as though even turning her head would give them both away, her eyes moved to the door handle - and relief washed the dread out of her when she saw that it was locked. Still, she wasn’t sure whether to feign sleep or see what her mother wanted. The needy throbbing of her fully hilted cock told her to resolve this predicament as fast as possible, and so Dia acted accordingly.

“Y-yes?” Dia called back in the steadiest voice she could muster. Hopefully she wasn’t giving away the fact that she was currently balls deep in her sister. Neither she or Ruby moved a muscle - aside from Ruby’s involuntary trembling - and suddenly Dia was aware of their ragged breathing. Their swift, forceful lovemaking had made the air in the room oppressive and hot.

The silence that followed was long enough to make Dia start sweating all over again. “Have you seen Ruby? She’s not in her room.”

Only now did Ruby turn her head, enough to make eye contact with Dia. Dia watched with bated breath, fresh fear shooting through her when Ruby began to raise her hips, inching deliberately off of Dia’s cock. Dia’s mouth fell open, seeing each individual strand of carnal juices clinging to her impressive length.

Still, Ruby said nothing. Dia’s cock was now fully outside, slick and shiny with Ruby’s juices. Dia bit down on her lip, stifling a desperate whimper. It took every ounce of control she had not to plunge every single inch of her cock back inside.

When Dia finally responded, her voice was thick with arousal.

“I-I don’t know,” she lied, her eyes still on the spot of their union. “Maybe she’s in the bathroom.”

Ruby’s eyes flashed with mischief. She wiggled her hips again, loosing Dia’s cock from its place against her labia. Dia inhaled sharply, her eyes greedily soaking up every detail of her sister’s body. In this precarious situation, where they were but one stray sound or moan away from being discovered, Ruby had the audacity to tease her? Dia’s brain was screaming at her to punish Ruby once more, to stop waiting for their mom to leave and fuck her sister senseless right this second.

A dirty thought wormed its way into Dia’s head. What if their mom _did_ hear them? How would she, or anyone else by extension, even react?

Dia herself wasn’t sure if she was acting out of curiosity, but regardless, she nudged her hips forward again. Ruby maintained eye contact as she was spread apart once more. Her pupils dilated and her walls eagerly wrapped and pulsatied around Dia’s generous endowment. A moan slipped out; it was probably from Dia herself, seeing as it wasn’t muffled in the slightest.

“Really? I thought the bathroom was empty,” their mom mused from just beyond the doorway. On their side, Dia continued to slide inch after agonizing inch inside Ruby. Dia clamped a hand over her mouth. Her cock pulsated desperately, asynchronously with Ruby’s insides, and the warmth and wetness was very nearly too much for her. She had to make a conscious effort not to blow her load right this second; there was no way either of them could keep quiet if that happened.

“I’m not sure… Maybe you could double-check?” Dia strained, her voice now muffled by her hand.

Again, their mom didn’t respond right away. While Dia waited for a response, Ruby slid down the final few inches of Dia’s cock. Dia threw her other hand over her mouth. Hopefully that was enough to mute the desperate, shameless moan that slipped out. She soaked in Ruby’s petite figure breathing heavily beneath her. The fact that Ruby, small and thin though she was, could accommodate her big cock and have a teasing glint in her eye while doing so made Dia’s head spin.

“You should spend more time with Ruby while you’re here,” their mom finally said. “She seems a bit lost without you.”

“O-of course, Mother,” she panted. Now fully sheathed, she bucked her hips forward uselessly. If they were at all lucky, their mother didn’t need to stick around any longer. Even so, Dia fought through the haze of lust to say one last thing.

“Ruby means the world to me.”

Dia was far too gone to even hear whether their mother had even responded, but she could tell when the footsteps retreated down the hall.

The moment Dia heard them round the corner, she whipped her head back towards Ruby, who waited with bated breath, Dia completely inside her. She pulled out abruptly and rammed her cock back in. Ruby arched her back violently, having her sister’s length shoved inside her all at once, stretching her out. But the moment Ruby turned around to implore her with her eyes, Dia used her free hand to press her face back into the bedsheets.

It was a somewhat awkward position for Dia, as she had to bend halfway over to find purchase on Ruby’s head while still fucking her, but it was important for Ruby to know that she would be punished for this. This position was even more tiring than yesterday’s, but it wasn’t for a lack of control - Dia could fuck her sister just as ruthlessly, but now she had to keep both herself and Ruby upright on her own strength.

Their union was as fast as it was depraved. The rhythmic slaps and smacks returned - Ruby’s ass would likely be quite red due to Dia’s pounding, if either of them had the wherewithal to look. For just this morning, Dia’s room was a haven of lust for older and younger sister alike. It housed all of their sighs, their wordless calls for each other, the hot, heavy air that mingled around them and hung stagnant over their forbidden union. At the center of this vortex of lust was, of course, Dia half-squatting over her sister, her sore legs shaking as her cock pistoned in and out of Ruby’s pussy. Ruby quivered beneath her, not even mustering the strength to speak as she was railed so roughly. Dia kept a firm hand on her little sister’s head, intent on taking full advantage of Ruby’s need to be fucked. The sight of Ruby so willing, so desperate to take her, caused her impending orgasm to surge forth.

Now Dia was certain - she had to cum inside Ruby again. Ruby was just so welcoming, so _tempting._ She’d been nothing short of shameless in presenting herself to Dia, even having the audacity to _tease_ her while Dia attempted to ward their mother off. So Dia was going to give Ruby her due recourse. Dia released her sister’s head, digging her nails back into her hips. What little control she had over her climax crumbled just as she hilted herself once more.

Only when Dia was sure that all eight inches of her cock were lodged inside of Ruby did she allow her climax to overtake her. Her cock pulsed powerfully, shooting rope after rope of warm, thick cum into her sister’s womb. Dia was bent at such an awkward angle, exhaling shakily, hunched over Ruby and half-squatting, half-standing. She didn’t care about any of that - she only cared about riding out the entirety of her climax inside. The overwhelming feeling of fucking her sister raw, cumming inside of her, having her balls pressed against Ruby’s slit, caused her entire body to tense up. She was riding on cloud nine - there truly was no better feeling than this.

Ruby hadn’t even needed to ask - Dia came inside her without hesitation. Though her face was still buried in the sheets, her sister’s presence was all around her and inside of her. Dia’s hot, ragged breaths glanced off of her back, growing louder and more desperate by the second. Similarly, Ruby’s breathing became more shallow the longer that Dia came inside of her. Her walls caressed Dia’s length, milking it, helping Dia deliver her seed into Ruby’s womb.

The feeling of Dia’s cum pumping into her was more than enough to send Ruby into a dizzying glee. She bit down hard on the nearest bunch of bedsheets, but that was hardly enough to suppress her wordless cries. She feebly pushed her hips back, even though Dia didn’t have any more cock to give her. Her legs shook, no longer possessing the strength to hold her upright. Dia’s firm hold on her hips was the only thing keeping her in place.

When Dia finally finished, she released her vice grip on Ruby’s hips, cringing when she saw the pockmarks her nails had left there. Ruby’s weight fell back onto her pelvis, and Dia grunted, having to steady Ruby’s body once again. Finally, she allowed herself to catch her breath. Several parts of her body were slick with sweat. For a moment, she didn’t move, lest she be overwhelmed by the sensations swarming her cock. A lewd mixture of their carnal juices now swam inside Ruby.

Dia pulled out with great care, inhaling sharply as Ruby’s walls clung to the now tender skin of her cock. She was already sensitive from the unexpected force of her orgasm, and the same went for Ruby and her pussy. Ruby wouldn’t be surprised if her pelvis and legs were sore from the time they’d spent clenched. She swayed back and forth on shaky legs as Dia released her, but was ultimately able to keep herself upright.

Once Dia pulled her softening cock from Ruby’s clutches, she found herself in a somewhat unseemly pose. Grimacing, she sank back to her knees. From here she could see the full extent of the mess she’d made out of Ruby. Aside from the new blemishes on her hips, there was an obvious point of attention. Dia’s cum drooled steadily out from Ruby’s lower lips, the perverse, physical proof of their love. Surely there was so much more still inside, in Ruby’s inviting and now-sensitive pink folds.

Meanwhile, Ruby had hardly moved. She simply stayed like that, legs shaking, face-down, letting Dia’s residual slowly trickle out for Dia herself to see. There was a warmth that spread inside of her. Even if she had been confident enough to move now, she didn’t want to as that would risk losing that primal warmth. It was as though she was showing off what Dia had given her, and the idea of Ruby being _proud_ of the railing she’d received at her sister’s hands was hot enough to send another wave of lust through Dia all over again. If her climax hadn’t drained her of everything, she probably would’ve dove right back in.

Both Kurosawa sisters took their time in catching their breaths. Try though she did, Dia couldn’t tear her eyes away from her seed dripping out of Ruby’s pussy. This was the second time in two days that she’d cum inside Ruby without a thought to the contrary. She needed to have a serious discussion about protection with Ruby at some point, though the incomparable bliss of barebacking her sister made Dia just as irresponsible as her.

Just when Dia felt the slightest of concern for Ruby’s well-being, Ruby began to stir. She pushed herself off her hands, coming to rest in a kneeling position. With her back still to Dia, she took a moment to undo her hair, and it fell slightly past her neck. Dia wondered momentarily if Ruby had done up her hair for the express purpose of seducing her, but when Ruby turned and they finally made eye contact again, she didn’t feel the need to dwell on it.

“Good morning, Onee-chan.” Ruby’s face was flushed from all that exertion. Her voice was tired but full of love, her bright green eyes the very same. “Did you sleep well?”

Dia blinked, caught off-guard by the simple greeting. “Y-yes.”

Ruby smiled. “You came so much,” she murmured breathily, contentedly. “It feels good.” Those words shattered the illusion of an innocent morning exchange.

Dia was scratching her mole before she even realized it. “I couldn’t help it.” She flushed - the base urge to have her way with Ruby felt a bit farther away now. “I just really wanted to finish inside you, and I got a bit carried away, and -”

Ruby closed the short distance between them, falling right into Dia’s arms. Dia closed her eyes, wrapping Ruby tightly in her embrace. “I loved it,” Ruby whispered into Dia’s shoulder. “When you cum inside me, it really feels like you’re mine, Onee-chan.”

Dia loved it too, but for the first time that day, her guilt stepped to the forefront of her mind. “Are you still on the pill?” she asked, fearing the answer.

However long actually passed before Ruby answered felt like an agonizing wait to Dia. When Ruby nodded into her shoulder, Dia released the breath she didn’t know she held. “I should’ve at least asked,” she sighed.

“I know you wouldn’t forgive yourself if we…” Ruby pulled back, running her fingers thoughtfully down Dia’s slender arms. “We did it unsafely. That’s why I’ve got everything covered.”

Heat rushed to Dia’s face as she remembered Ruby’s morning greeting - her soaked nethers begging to be ravaged. As primally and impulsively Dia had acted at the perverted sight, immediately pouncing on her sister, Ruby probably put a lot of thought into preparing beforehand. “I can help. I’ll set reminders and alarms and the like.” She scrambled to make up for thinking only with her cock.

Ruby only giggled, brushing her fingers across Dia’s breasts, making her jump. “Thanks, Onee-chan,” she said simply. She crawled back into Dia’s arms. Dia treasured Ruby’s warmth. They lay down together, but instead of snuggling up to her sister’s side, Ruby straddled Dia, nestling her head into the crook of Dia’s neck as she rested atop her.

Now that she’d given her all to Ruby, Dia finally let herself think about what just happened. Their lovemaking was so primal that Dia could hardly think of it in those terms. She truly did surrender herself to her senses in those moments: Ruby shaking and quivering beneath her, the sweat rolling off of them, the heaviness of the air, and most of all the warmth of her sister’s pussy. The depravity that she shared with Ruby could probably be likened to breeding _,_ or even mating.

Of course, mating with her sister in their own house posed a number of problems, one of which they’d just run into.

“I can’t believe you teased me like that. When Mother was at the door,” Dia murmured, running a gentle hand through Ruby’s hair. “That was…”

“...Bold?” Ruby whispered, her fingers trailing Dia’s collarbone.

“I was going to say ‘reckless,’” Dia sighed. “What if she’d heard?”

“I don’t know,” Ruby hummed. “What _if_ she’d heard?”

Dia flushed. “T-that’s…”

“You were thinking of it too, right, Onee-chan?” Ruby continued. Dia heard the playful lilt in her voice. She sighed - she didn’t know why she still tried to hide things from Ruby. Now that they’d bared their bodies and souls to each other, there was no reason to.

“I was, in an irrational sense,” Dia admitted.

“Was it exciting?” Ruby asked plainly.

Dia rolled around her response in her head. She already knew what she’d say, but it was still embarrassing. “If it wasn’t, I wouldn’t have kept fucking you.”

One of Ruby’s hands traced Dia’s side, falling lower and lower. It landed right on her hip. “I’m glad you did.” Ruby’s breath grazed Dia’s neck, making her draw in a breath. “It excited me, too.”

“Only in theory,” Dia confirmed. Ruby nodded.

They were both forced to confront the newfound hot air in the room. Once again, Dia cursed her lack of foresight in forgetting to bring a fan. Drained yet fully satisfied, they lay there, still intertwined and panting heavily. Content though Dia was to lay there, her mind had other plans.

“I’m glad that you took the leap first,” Dia said. The image of Ruby in revealing lingerie, still fresh in her mind, stirred lust and overprotectiveness in her in equal parts. “If you’d shown that side of yourself to anyone else, I…” She trailed off. She didn’t know what she would’ve done, and the mere possibility of that scared her. As a result, she hugged Ruby even tighter.

Ruby sighed happily, enveloped in her sister’s protective embrace. She really did treasure her sister’s warmth all around her and inside of her. “Me too, Onee-chan. I just thought you might’ve been done waiting. I was too.”

“You’ve been nothing short of wonderful, Ruby,” Dia grunted softly as Ruby shifted on top of her, pressing their bodies close. Perhaps the lingering musk of their lovemaking was getting to her head, bringing another base thought to her mind. “Besides…” she continued, now softer.

“Besides what?” Ruby murmured.

“No one can fuck you like I do.”

“That’s my Onee-chan.” Ruby giggled, kissing Dia’s cheek. “You know all my weak spots.” When she moved in again, Dia turned to meet her, and they shared a slow, languid kiss. When Ruby’s lips parted, Dia slipped her tongue in and they mingled freely. When they pulled away, Ruby’s eyes sparkled with satisfaction and content. Dia could only hope that the same was reflected in her own eyes.

They cuddled in silence. Dia stroked Ruby’s lovely red hair, her heartbeat slowing to its usual pace. She felt the same from Ruby’s chest. Every so often, another trickle of Dia’s cum would escape Ruby, and each time Ruby shivered. They were sticky all over and their nether regions were soiled, but if Ruby was content to lay there without cleaning up, Dia was too.

“Onee-chan.” Ruby spoke up after some time had passed.

“Hm?”

“Can I come visit you in Tokyo?” Ruby propped her chin up on Dia’s chest, her green eyes shining with hope. “There’s still so much I want to see there. And…” she looked away.

“...We’d have more time alone?” Dia finished for her.

Ruby nodded shyly. Even if Dia was inclined to disapprove, she would’ve had a hard time saying no when her sister adopted that look. Besides, they had many more missed chances to make up for. She pulled Ruby close once again, placing an affectionate kiss on the top of her sister’s head.

“Of course, Ruby. Anything for you.”


	3. Here With You

**Summary for the Chapter:**

> After months of being apart from one another, Dia and Ruby jet off to an island resort to spend some quality time in each other's arms. All they need is a bottle of champagne and each other.

**Notes for the Chapter:**

> hey y'all - meccha here. yes, i know we keep marking this fic as complete and then adding more to it anyways. how can i resist when these two are so perfect together? i got the idea for this lastest entry from my collaborator from the first chapter, and i couldn't resist jumping on the chance to have them skinny dipping together and all that romantic stuff that i love. the tone is a bit different as a result, but i think they've earned some romance. :') hope y'all enjoy.

In the hazy streets of Tokyo, choked with a cacophony of noises and suffocatingly grey, time seemed to move less on the scale of days and months than it did on the scale of milliseconds. When Dia had first arrived as a bright-eyed college student she’d relished her time here, even with all the fears that came alongside such a huge metropolis; that had all changed, however, with her first winter break. With a newfound lust for her little sister had come a longing to be closer to her, transforming Tokyo from a mecca to a prison.

Once she’d been forced to return, the intervening time until they saw each other again began to stretch on and on, hardly abated by the scattershot day trips Dia was able to take home between all her busy work. It was difficult to do much of anything with Ruby knowing that their parents were home, not after the close call they’d had prior. They were forced to content themselves with clandestine sexts and video calls, their sole source of relief for all those months of pent-up lust.

December became January and January melted into February in a frigid blur. Ruby celebrated Dia’s birthday with a panoply of nudes she’d nervously taken on the beach near Kanan’s place one evening, her nipples hard by the cold weather. February was soon March, and Dia regaled Ruby with all of the holes she’d be fucking for spring break as punishment for Ruby’s lewd behavior. Spring dragged along painfully, all of Dia’s bones screaming for Ruby’s touch as she put herself through hell in order to finish the year in good academic standing. Business school was hardly conducive to her love life, leaving the two of them with little time to share together until Dia was able to spirit away to her bedroom for an hour in order to call Ruby.

“Show me how wet you are, Ruby,” Dia practically _growled_ as she watched her little sister hike up her painfully short skirt to reveal the large damp patch that was steadily spreading out across her panties. She whimpered quietly as she did so in a play at innocence, but Dia knew better. She stroked herself in full view of the webcam on her laptop as she watched, an unyielding harshness to her voice as she spoke.

“You’re such a slut, Ruby. Don’t pretend like you’re not enjoying this.”

Ruby smiled clandestinely as she pulled aside her panties, revealing the glistening folds of her labia.

“Maybe, but only because _Onee-chan_ taught me,” she crooned sweetly in reply. Her tongue lingered on the word Onee-chan, letting its forbidden quality ring out through the tinny microphone and into Dia’s room.

“Do as I say, Ruby,” Dia countered. She was painfully hard by now, her erection sensitive to even the gentlest touch from lack of attention paid to it in favor of Dia’s exam work. She imagined how perfect it would feel in Ruby’s warm, soft, wet mouth, her tongue caressing its head tenderly - Dia’s hand paled in comparison, but it would have to do.

“But I think I prefer what you _do_.~” Ruby let out a sound halfway to a purr as she stuffed a finger in her pussy, pumping it slowly as it was coated liberally in her slick. A second soon followed, and Ruby took the opportunity to use them as leverage with which to spread her pussy for the camera, hoping beyond all hope that her actions would rile Dia up further. “I want you so badly, Onee-chan…”

“ _Fuck_ ,” Dia muttered under her breath as she saw Ruby bare her insides so shamelessly. She felt herself throb in her grasp, and she started stroking herself harder. “As soon as school lets out I promise you can visit me, Ruby. I’ll fuck you into a good girl.”

An unnatural silence followed, masked only by the quiet _schlick_ of the two pleasuring themselves for one another. It was as though Ruby was lost in thought, even as she continued to fuck herself.

“What if we don’t have to be in Tokyo, Onee-chan? Or here too?”

Dia paused in consternation at Ruby’s curious choice of words, her hand coming to a stop yet all the while resting on her cock.

“What’s wrong with either of those? Do you not want me to take you on your bed anymore?”

“Well… our parents,” Ruby explained bluntly. Dia’s mouth formed a small O as she considered. “And you said your apartment has thin walls.”

“Ah. You’re suggesting we go somewhere, then?”

Dia began stroking herself again slowly, beginning the process of building herself back up to the blissful plateau she’d been skating prior to this turn in the conversation. Ruby had begun fondling one of her petite breasts, riling Dia’s imagination as she imagined her mouth suckling at and biting Ruby’s cute, pert nipples.

“I’m graduating, so our parents would pay. I… did always want to visit Okinawa ever since Kanan taught me how to dive,” she added coyly. Dia raised an eyebrow.

“Kanan didn’t teach you anything else, did she?” There was a subtle yet nonetheless possessive edge in her voice, as if the thought of some harlot such as Kanan coming within a five mile radius of _her_ little sister was entirely unacceptable - and it very much was. Ruby seemed to pick up on her defensiveness, however, and spoke next in a teasing tone of voice even less acceptable to Dia’s ears.

“Maybe with a week all to ourselves, you could find out,” she playfully replied, speeding up her fingers as she fucked herself eagerly for the camera.

Dia ate up the sight, knowing perfectly well that she was falling victim to her little sister’s disconcertingly bottomless capacity for plying others to her whims. First she’d goad Dia into saying yes, then their parents next - there was no point resisting, not when all Dia wanted to do was plunge her cock inside the dripping wet pussy taunting her from the other side of the laptop screen. Her jealousy over Kanan’s proximity to Ruby could come later - her maddening erection was much more important for now.

“I’d like that,” she replied lazily as she reached her orgasm, painting her hand and bare stomach in thick ropes of cum. Ruby followed soon after, screaming out Dia’s name into her microphone as she squirted all over her fingers. The two of them were left to bask in a hazy kind of glow, but one that paled in comparison to the feeling of laying side by side.

In that moment, Dia figured that perhaps a vacation was exactly what the two of them needed.

/-\\-/-\\-/-\\-/-\

The plane came in choppy, and Dia gripped the armrest with an intensity she would be embarrassed to admit to a soul. She would’ve been plenty happy ending her journey in Okinawa like Ruby had originally suggested, but when their parents had caught wind of their planned vacation they’d insisted on something _far_ nicer, settling on a remote onsen located on the small island of Aharen. That meant a prop plane, and Dia’s comfortability with travel was tested as a result.

Still, the choice of location had its upsides. This was as far as the two of them could have gotten from home without trekking into the jungle, and with that distance came freedom from the burden of family. Here, Ruby and Dia weren’t Kurosawas - they were young lovers, intent on spending the perfect week in each other’s arms.

Fittingly, as soon as Dia got off the plane and walked the tarmac to the tiny building serving as the airport, the first thing she saw was that unmistakably pitch red mess of hair she knew and loved so well. It was worn down currently, a small braid circling behind her head as though it were a crown. She wore a sundress of radiant blue, making her seem right out of a watercolor in even the sterile light of the baggage claim. While on any other occasion Dia might have been subtle about her joy, this was no time for it; she raced forward with a bright smile on her face, only slowing down to secure her purse to her body before she scooped Ruby up into a tight hug, holding her tight.

“I missed you so much, Ruby.”

“Onee-chan,” Ruby whispered as her head found its place in the crook of Dia’s neck, nuzzling into it like a baby bird seeking shelter in its nest. A soft coo murmured against Dia’s neck sent her skin crawling, and shortly after Ruby raised her head to look Dia in the eyes.

And then, before Dia could even think, Ruby pulled her into a deep, longing kiss. At first, Dia panicked - how could she not? - but as it went on she felt a sense of comfort in the way that Ruby held her through it, an unspoken message of reassurance. It was okay, Ruby seemed to say. Nobody knew.

And that was enough for Dia to let go, melting into her sister’s embrace as she returned the kiss, slow and tender. All her tensions from the plane ride evaporated from her bones in an instant, replaced by the love she felt for Ruby and the overwhelming desire she held in her heart. Around them the other passengers went about their days, entirely uninterested in the pair of young lovers before them.

The ride to their residence for the next week was thankfully much easier than the plane ride, choppy winds exchanged for gorgeous vistas as they wound their way around the island in a rental car, the windows down and wind rolling through their hair as they made their way onward, sandwiched between the endless expanse of the ocean and the towering, verdant mountains. On the radio blared some cheesy pop song that happened to be playing over the airwaves, but it was lost to their ears as they focused on the breathtaking views unfolding before them. Idly, Dia took a hand off the steering wheel to rest it on Ruby’s thigh, turning for the briefest moment to offer up a smile that was warmly reciprocated as Ruby laced a hand together with Dia’s, their fingers intertwined.

After winding their way up the mountain, the onsen their parents had booked came into view, perched atop an incline that led down to the ocean below via a narrow staircase that seemed almost treacherous. At the bottom, however, stood a pristine white beach shielded from view on all sides by rocky outcroppings. Dia stopped for a moment to take in the view, but the sojourn was briefly lived when she realized that they had a check-in to attend to.

As it turned out, she’d had no need to stall - their parents had splurged on a room with an ocean view of its own and its own private onsen, a world away from even the rest of the island. No sooner than they’d stepped inside did Ruby begin fawning over the grandeur of the place, rushing out to observe the view and take in the private spring that bubbled forth from the terrace. Dia smiled warmly as she looked on Ruby’s backside, taking her time as she dropped her luggage off and strode towards Ruby, who was perched over the balcony looking down at the ocean. In the distance, the sun was just beginning to dip below the horizon, bathing the ocean in golden hues of oranges and pinks.

Perhaps it was the romance of the view, or perhaps it was her sister’s innocent, wide-eyed allure that prompted Dia to wrap her arms around Ruby’s waist from behind, pulling her close and prompting a quiet giggle from Ruby’s lips as she brought her mouth to Ruby’s ear, taking a slow breath.

“You look so beautiful in this,” she whispered as she gripped at the fabric of Ruby’s sundress, running her hands all along it until they found their perch on Ruby’s breasts, groping them gently. Sensing only fabric beneath the dress, Dia found the corners of her lips curling up. “A bralette, Ruby? Oh, you never learn,” she remarked sarcastically as she pinched Ruby’s nipples.

A breath of a moan signalled Ruby’s assent to the act, and Dia wasted little time in progressing. She peppered kisses across Ruby’s neck and began dropping one hand lower, pressing it between Ruby’s legs through her sundress to rub at the area between them.

“Onee-chan…” Ruby whispered, squirming in Dia’s grasp with little desire to do anything other than submit to her sister’s advances. “Take it off of me, please.”

Dia reached down to draw the dress upward from Ruby’s body, pausing only to check and make sure that they were shielded from view - and indeed, it was impossible for anyone to see them from up here. Safe in the comfort that their privacy was secure, Dia removed herself from Ruby only long enough to pull the dress all the way off, using the chance to run her hands up Ruby’s bare skin until she was vulnerable and exposed, little more than her lingerie to shield her body from the elements.

And it was deeply, deeply familiar lingerie.

Beneath her dress, Ruby wore the bralette and thong that she’d put on when she first seduced Dia the winter prior, all pink and flowery and alluringly transparent. What little of the fabric that was opaque was flourishes of silk like flowers, accomplishing little other than to frame her breasts in all their petite, perfectly cute glory.

“I see you stole my bra again,” Dia murmured against Ruby’s neck with a half-smirk. “You’re so shameless, Ruby. I expected better of you by now. What do you have to say for yourself?”

Ruby tried to open her mouth to respond, but before she could utter even a peep Dia slipped a hand into her thong, rubbing a finger against Ruby’s labia and provoking whimpers of arousal all the while.

“No words, hmm?” Dia crooned, not quite mocking yet still with some semblance of a bite. “Perhaps I should indulge you then, since you’re apparently too far gone to do anything other than take me.”

With that, a finger slipped inside Ruby’s soaked pussy with ease. Ruby moaned and called out Dia’s name, hushed not even by the fear of another resident at the onsen being able to listen in on their clandestine activities. Thinking quickly, Dia hooked a hand around to Ruby’s mouth, shoving her fingers inside forcefully.

“Be a good girl and stay quiet, Ruby. Or do you want them to know how much of a whore you are for your sister?”

Ruby shook her head, at least as much as she was able to given the way Dia was violating her personal space.

“That’s what I thought,” Dia whispered as she began pumping her finger in and out of Ruby, then a second. “Just let onee-chan take care of everything, okay?”

Ruby mewled and whimpered into Dia’s fingers, up until she gave up and began suckling on them instead. The sensation aroused Dia like never before, and she renewed her efforts, pumping her fingers rapidly in and out until it was clear that Ruby needed more to push herself over the threshold of orgasm.

Dia could have put her erection to use, but no - they’d only just arrived, and she was hardly one to spoil her little sister. A true fucking could come with time, but for now she wanted to make sure Ruby was at least somewhat sated, so she instead began to push a third finger inside. Ruby cried out at the newfound girth, but it wasn’t from pain - no, she’d had Dia inside her far too many times by now to struggle with three measly fingers. Instead it was from arousal as she was finger fucked.

A thumb pressed against her clit over and over again until Ruby eventually came violently, her body shaking as she leaned over the railing, squirting all over one hand and drooling on the other. It was a humiliating sight, and one that had Dia throbbing against her slacks as she pulled herself outside of Ruby and allowed her sister to catch her breath.

A quick kiss on the head signalled Dia’s affections before she trailed back to the room, using Ruby’s afterglow as a chance to prepare a small celebration for the two of them. Inside the living room on the table stood a bottle of champagne, compliments of the onsen - perfect. Dia deftly uncorked the bottle, doing her best to muffle the sound with a hand and catch the cork so as not to startle Ruby. She poured two flutes and grabbed one with each hand, bringing them back to the patio where Ruby had already recovered slightly, panties pulled back up and quim wiped away with a spare towel that had been laying nearby.

Smiling playfully, Dia held the flutes up and handed one to Ruby.

“Don’t tell mom and dad, okay?”

“Of course,” Ruby replied with a quiet giggle.

The two of them whittled the last of the evening away like that, lounging on the patio and sipping champagne together as the sun sank beneath the Pacific and took the vibrant colors of the sky with it. In their place came the cool blues of the night sky, mottled only by the milky way as it unfolded before their eyes. This far from the bustling cities of the Japanese mainland, there was little to prevent them from beholding the sheer beauty of the night sky above them, and they both reveled in it. Eventually, Dia thought better of her stuffy travel attire and got up long enough to shed her clothes, revealing a beautiful set of black lingerie that she’d picked out for the occasion. The pushup bra she wore made an appetizing meal out of her breasts, and the garter belt framed her silk panties and held her stockings up tightly. Ruby looked onward at the outfit and smiled, beckoning Dia back to the couch they’d been sharing together.

“Want some more champagne?”

Dia nodded, but before Ruby had the chance to reach for the bottle she found herself pulled into a deep, passionate kiss. Guarded by little more than the suggestive lingerie that they wore, their skin rubbed together and hands roamed each other’s bodies. Dia had held out for so long, but here before the vastness of the ocean she could wait no longer. She wanted Ruby more than she’d ever wanted anything, and she knew that Ruby wanted her too. Her desire was apparent, too, as she felt her erection grow until it was straining against her panties. A hand quickly rushed down to adjust and allow it to slip above the waistline of her panties, pinned against her stomach.

Ruby quickly realized what Dia’s hand had been doing, and she wasted no time in tracing the line it had made with her own, wrapping her dainty fingers around Dia’s shaft and pumping it lazily. Dia groaned into Ruby’s lips at the contact, but before she could push herself further into Ruby’s grasp, Ruby pulled away.

“Let me pour you some more champagne first, onee-chan.”

Dia felt herself frustrated, but she could only nod in reply, taking the flute as soon as it had been refilled and pressing it to her lips. The sting of the carbonation felt refreshing against her tongue, as did the gentle buzz in her head as the alcohol performed its magic, numbing her senses just the slightest bit and dulling the inhibitions that so often clouded her mind. In their stead was pure adoration for her sister, unadulterated by the shame that often held it down. She stared longingly at Ruby’s nearly-bare form, desperate to explore it for longer, but Ruby had other plans.

As soon as she’d set the bottle down. Ruby sprawled herself across the couch, resting her head on Dia’s lap - precipitously close to her erection, which was as hard now as Dia could bear.

“Let me take care of this for you onee-chan,” she cooed sweetly. “Just relax and enjoy yourself, okay? Let me be a _good sister._ ” Any ambiguation to the meaning of her words was quickly dispelled when she leaned to Dia’s cock and pressed a kiss to the shaft, prompting a shudder to crawl its way across Dia’s skin.

“Well, if you insist,” Dia replied, a bloom on her cheeks that she was desperate to hide. “I can’t say no to you knowing your place, can I?”

Ruby just giggled as she pulled Dia’s panties down a bit further, enough to give her more leverage with which to pull it away from Dia’s body and wrap her lips around its head. They formed a seal that drifted further and further down Dia’s shaft until Ruby had taken it all into her mouth, only a swallow to indicate that she had any trouble doing so. It was evidence of the sin they’d enveloped themselves in with every single visit over the last half year that her mouth was so deft at pleasuring Dia. It wasn’t just another warm hole - it was an instrument, one that Ruby used readily.

Dia whimpered and groaned as Ruby began to bob her head up and down, but she was intent on not wasting the moment she’d been provided. Her gaze drift from Ruby to the serene seascape before her, enjoying the view of the stars and the waves illuminated by ethereal moonlight as she sipped away at her champagne. Only occasionally did she acknowledge Ruby’s efforts with a word or two of praise, but it was enough to keep her sister going all the same.

Eventually a hand threaded itself into pitch red hair to guide her up and down Dia’s cock more swiftly, the only sign that she was impatiently waiting for the blissful high of orgasm. Ruby readily assented, speeding up her actions until at last she felt Dia twitching within her mouth.

“Swallow for me, Ruby,” Dia whispered warmly, and with little other warning she shot her seed directly into Ruby’s mouth. The sensation of Ruby hastily swallowing it all only increased the intensity of Dia’s orgasm, and by the time she finished, the hand still holding her champagne was shaking ever so slightly.

Up there in the night sky that draped over the island like a canopy, the stars twinkled and shone brightly, almost as though they were beckoning Dia forth. Once Ruby had lifted herself from Dia’s cock and wiped a stray rivulet of come from her cheek, Dia leaned down to place a loving, tender kiss to her lips.

“How are you feeling, Ruby?” she whispered.

“A little sleepy,” Ruby admitted sheepishly, “but good. Really good.”

Dia smiled warmly.

“Why don’t you lay on my lap a while longer? We can go back inside in a bit.”

“That sounds nice,” Ruby replied. Her words were vacant, signalling her exhaustion, and before long she was out like a light, nuzzling into Dia’s lap with a soft smile painted on her cherry lips.

Dia giggled to herself faintly. Eventually she’d bring Ruby to bed, but for now she could enjoy the view a bit longer. Reaching to the table in front of them, she grabbed a spare blanket and unfurled it, draping it over Ruby. Idly, she sipped at the last of her champagne and wondered just what she’d done to deserve such a perfect sister.

/-\\-/-\\-/-\\-/-\

Their vacation waned in fragments, fits and starts of excitement and passion breaking through the hazy, slow rhythm of a spring that felt more like summer than anything else. Afternoons were spent on the beach, exploring the town, enjoying the public springs, anything the two of them could do as long as they did it together. Evenings, meanwhile, were spent in the throes of passion. Dia took Ruby anywhere and everywhere she could - in their private onsen, on the couch, in their futon. It was all fair game, and the two of them reveled in the freedom they had to shower one another in affection and love. Nights were spent in deep slumbers, the two of them always wiped out from the day’s activities and from hours of passionate lovemaking.

Only once did Dia break from Ruby’s presence, and not by choice. Rather, she had something she needed to do. They’d dedicated their last day there to relaxing, taking a break from all their exploration to lounge and enjoy their room to its fullest extent. Ruby opted to whittle away the afternoon on the patio, content to bask in the warmth of the sun as she dozed in and out of consciousness. Seeing that Ruby was off in the world of dreams, Dia smiled to herself and placed a kiss to Ruby’s forehead.

_Gone into town for a few things, won’t be long. -Onee-chan_ , read the note she placed on the table. Grabbing her purse and slipping on a pair of pumps, Dia hopped in the car and made her way to the edge of the nearest town, where opportunities to shop were few and far between. It was a lot like Uchiura in that respect, a thought that was somehow comforting. She wasn’t free of options, though, of that there was little doubt in her mind - she’d passed by one particular shop more than once with Ruby already, eyeing a particular piece in the window display all the while.

It was a little hole in the wall jewelry shop, full of pieces more dazzling than one would expect to find in such a remote place. It took a few minutes of browsing and conversing with the shopkeeper, but eventually Dia was able to sort through the myriad of rare metals and gemstones to find what she wanted.

“Just this, please,” she told the shopkeeper as she brought it to the counter. It was a silver necklace, unassuming yet elegant. On the end of the chain was a heart, embedded with two tiny gemstones - a diamond and a ruby.

As soon as Dia was checked out, she placed it gently in her purse and made her way back to the hotel. Ruby had stayed fast asleep, and with a humored look Dia grabbed the note and tossed it out before Ruby could see it. She roused her sister from her peaceful slumber with a kiss, wriggling her way onto the couch so that they could cuddle together for a while, even if there was barely enough room. Ruby just smiled and wrapped her arms around Dia lazily like she might hug a giant teddy bear, and kissed her all over.

The two of them stayed like that for what felt like an unbounded stretch of time, focused on little other than the comfort that they brought to one another as they laid in each other’s embrace. Ruby was the one to interrupt it, a mischievous glint in her eye as she pressed a kiss to the shell of Dia’s ear.

“Wanna go swimming?”

/-\\-/-\\-/-\\-/-\

The cove beneath the hotel was remote, all kinds of rocky outcroppings to hide beachgoers from view. Anyone who wanted to be truly alone, invisible to the rest of the world, had little trouble doing so here. Ruby had apparently already done some scouting of her own, trailing down the beach a ways until she showed Dia a serene little beach that couldn’t have been much larger than a small house, flanked on both sides by cliffside and only a narrow trail along the beach leaving it accessible to the outside world.

In her hands Dia carried beach towels and a few recliners inside a large tote bag, while Ruby lugged a small cooler along. It was everything they needed for an evening under the stars, and soon they were lounging side by side, enjoying the way that the ocean’s breeze pierced the warm tropical air. Ruby poured the two of them glasses of pinot noir, sipped away like the evening itself.

“I wish we could stay here longer,” Ruby finally said. “I’m scared of going home.”

Dia knit her brows. “Because of university?”

“Because we can’t be like this any more.”

“... Ah.”

The acknowledgement left Dia’s mouth with a dull thud as reality suddenly began staring her in the face. Ruby was right - this trip had been their own little slice of heaven, but it had to come to an end. All these things they’d shared with one another - holding hands, kissing in public, making love - would be taboo once again, clandestine and secretive. They would just be two sisters with a secret.

Dia abhorred the very thought.

“Can… can I ask you something, onee-chan?”

“What is it, Ruby?” Dia turned to her sister, who was taking a shaky sip from her wine glass. Ruby didn’t dare return her gaze.

“Are you going to find a girlfriend when you go back to college?”

Ruby looked so sad where she should’ve been at peace. Her eyes were downcast, yet they should have been full of light like life itself.

“Oh, Ruby…”

Dia sat up and maneuvered herself onto Ruby’s chair, straddling her body and leaning in for a soft, gentle kiss. Ruby tasted like the faint acidity of wine, and a thumb that reached to stroke Ruby’s cheek felt a distinctive dampness there.

“The thought of you giving yourself to someone hurts,” Ruby admitted in a whisper. She looked up to Dia with wide eyes filled to the brim with vulnerability, and the sight reminded Dia so much of the day she graduated from high school. “When we were kids we said we’d be together forever. I guess I never let go of that idea.”

“You don’t have to,” Dia replied. Ruby only stared, unsure of Dia’s intent until Dia reached into the tote bag beside them and pulled out a small jewelry case. “Open it, Ruby,” she whispered lovingly as she passed it to her sister.

Inside was the necklace she bought, diamond and ruby embedded side by side there in the heart’s grasp. Ruby gasped as she saw it, and she looked to Dia with an ever-growing smile on her face.

“It’s… it’s beautiful.”

“It’s my way of promising that I’ll always be yours, Ruby. And you’ll be mine.”

In only a moment Ruby had locked the two of them into a passionate embrace, and it took Dia a moment to realize exactly why - there on her shoulder, Ruby was crying. She was letting out all her anxieties and fears, all her overbearing jealousy towards those who kept her sister away from her. It came out in a torrent, and all Dia could do was hold Ruby tight and whisper sweet nothings, declarations of unconditional love and devotion.

Once Ruby calmed down, Dia pulled herself away, but only for a moment - just long enough to place the necklace on Ruby, clipping the chain shut and running a hand along Ruby’s collarbones to admire its place there against her bare skin.

“There, perfect,” Dia said sweetly. “It looks gorgeous on you.”

Ruby let out a faint giggle at the contact, and experimentally Dia let her hand ghost lower, cupping one of Ruby’s breasts. The action elicited a breath of a moan, and it didn’t take long before Ruby was helping to facilitate it. A cloying look on her face entirely mismatched with the tears that had streaked her cheeks only moments before, she reached her hands behind her back to undo her bikini top and tug it off. Dia began lavishing Ruby’s breasts with affection, kisses and love bites mottling her skin, but she always made sure to return to that necklace, kissing all around it and doing everything to remind Ruby of its meaning - that they were only whole when they were one.

The rest of their swimsuits came off not long after, tossed aside with little pomp or circumstance. They were just pieces of fabric keeping their bodies from one another, after all. Ruby grasped at Dia’s erection between them, pumping it eagerly as Dia slavishly devoted herself to showering Ruby with her affections. Both of them were aroused beyond measure and desperate for one another, but the night was still young and they both knew it. Perhaps it was the sisterly bond they shared that prompted them to slow down in unison - a single glance was all they needed to convey their intent as Dia sat up and grasped Ruby’s hand, pulling her up in turn and leading her to the water.

It was cold to the touch, and the two of them squealed as they came into contact with it, devolving into laughter. Eventually they adjusted to it well enough however, and they waded deeper into the Pacific’s embrace, hand in hand.

“Let’s come back here soon,” Ruby spoke softly.

“We can go anywhere you want, you know,” Dia replied. She paused, laughed to herself. “Well, as long as you keep your grades up. Being a whore can’t always come first.”

Ruby flushed at the acridness of the word, but quickly joined Dia in amusement. After a moment, she stuck her tongue out and pulled Dia farther out. Any other day Dia would be hesitant to test the waters like they were, but tonight the ocean was placid. It gently rolled back and forth, bending and refracting the moon’s rays into an endless field of shimmering light that stretched out before them.

When the water came up to their thighs, Ruby turned back to Dia and gave a smile that fended off even the chill of the ocean, warming Dia all the way to her core. Giving in, Dia embraced Ruby and brought her in for a deep, passionate kiss. Her tongue snaked out from parted lips to claim Ruby’s mouth and explore its contours deftly, and Ruby moaned in response. A hand dipped down Ruby’s backside and pawed at her ass. It was an unmistakably possessive act, one that told Ruby she was Dia’s and nobody else’s. Ruby’s leg lifted upward and wrapped itself around Dia’s waist as an answer, the act enough to stoke the fires of Dia’s arousal.

Between Ruby’s legs, Dia felt herself growing erect, and without even thinking she began grinding her cock against Ruby’s labia. She let out a low groan, resisting every instinct her body carried with it to plunge straight in and fill Ruby. Instead she took her time, winding her sister up further and further until Ruby’s whimpers and mewls became more desperate, melting into pleas for Dia to complete her.

There under a night sky not that much unlike the one they’d shared growing up in Uchiura, Dia pressed herself inside Ruby. Being inside her felt like home, so familiar as to be a second skin. Slowly, methodically, Dia began pulling out and pushing back in, just enough to reacquaint Ruby with her girth and size. It was a tradition that likely wasn’t needed by now - Ruby was far too wet to worry about things like that - but it was nevertheless important. It was how Dia expressed her devotion to protecting Ruby, always the perfect model of a big sister.

Still, it was clear when Ruby needed more - that much was evident in every noise that escaped Ruby’s lips. Ruby knew how to ask for what she wanted, and Dia was always happy to provide. She began moving with force, tightening her grip on Ruby’s ass to hold her up and pulling her closer for extra leverage as she began thrusting inside. Not content to be the only one bearing marks of their time together, Ruby’s nails painted works of art down Dia’s back, and she stifled her cries by biting down on Dia’s neck, leaving hickeys all over. Dia’s thrusts became ripples of water that lapped at their bare legs, as if attempting to pull them down further into the depths of depravity.

“I love you, onee-chan,” Ruby murmured into Dia’s skin, the words becoming vibrations that traveled all the way down to her core. “I love you so much.”

“I…” Dia’s voice gave way to a labored grunt as she bottomed out in Ruby yet again, and she took a moment to savor Ruby’s warmth there inside of her. “I love you too, Ruby,” she finally spoke. She pulled away, if only to reach between them and cup Ruby’s necklace in her fingers, bringing it up to her lips to place a kiss upon it. “I’ll always love you.”

In truth, she wasn’t sure what their relationship meant now. Were they sisters, or something more?

Perhaps they could be both, but that mattered little when they were still joined to one another, both desperate for release. Dia wasn’t the only one who was painfully aware of that fact - in pursuit of relief, Ruby began grinding back down on Dia’s erection, doing all the work that Dia had been doing prior. There in the moonlight, naked and bared with only the necklace to cover her, Ruby looked angelic as she pumped herself up and down, up and down.. It was pure will that prevented Dia from pulling her close and thrusting away with abandon, but she was so enraptured that she would have undoubtedly struggled to do anything Ruby didn’t want in that moment anyways.

Eventually, Ruby’s movements began to coax Dia closer and closer to her breaking point, and through feverishly shaky movements Dia moved a hand between them to rub at Ruby’s clit in the hope of pushing them over the edge at the same time. Ruby let out a mewl of desperation as Dia rubbed steady circles over and over again, and soon neither of them could take much more.

“Please finish in me, onee-chan,” Ruby murmured tenderly. Those words were enough to push Dia over the edge, and she obeyed without a word. As soon as her muscles untensed, she shot all of her seed directly into her sister, load after load leaking out and dripping down into the ocean below. All the while Dia renewed her efforts on Ruby’s clit, and after a moment longer her sister came as well. Her body shuddered in its entirety, gooseflesh prickling up and consuming her body as she fell into Dia’s embrace. Dia held her tight through it all, whispering tender words of love into Ruby’s ear as Ruby shuddered in her grasp.

Finally the two of them fell away, sore and aching and in absolute bliss. Dia pulled herself out of Ruby gingerly and pulled her in for a passionate kiss, before grabbing her hand and leading her back to the beach. There, under the moonlight, they returned to their beach chairs and wine glasses, intent on enjoying the last waning hours of their vacation hand in hand.

“You know,” Ruby said after a moment or two cloaked in silence. “I’ve been thinking about the next year.”

Dia turned her head, an eyebrow cocked. “What about it?”

“Well… I’ll be studying hard, of course,” she started with a cloying smile, clearly intent on winning Dia’s good graces. “And maybe if I study hard enough, I can transfer to a less local university. Somewhere in the big city, where I have someone I can live with in a nice little apartment.”

The corners of Dia’s mouth curled upward as Ruby spoke, coming to a crystal clear understanding.

“A one-bedroom apartment, I assume?”

“Yeah, with a nice, comfy mattress,” Ruby replied playfully. “And a huge closet full of outfits that will drive my girlfriend wild.”

_Girlfriend_. The word landed with all the weight of an anvil between them as soon as it had been uttered, and it took a moment just to process the weight of its meaning.

“Well…” Dia eventually spoke, her words slow and methodical. “I suppose you’d need a girlfriend then. Someone who will look after you and treat you the way you deserve. I don’t trust just anyone to do that, you know.”

Ruby looked Dia in the eyes, her irises a vibrant emerald.

“Shut up and kiss me, onee-chan.”

Tomorrow the Kurosawa sisters would have to pack their belongings and fly home, separate once again and longing for each other’s touch. But no matter how great the distance, this time they had something that could bridge the yawning divide between Nuzamu and Tokyo - their love for each other.

So they spent their final evening in paradise wrapped in an embrace, sipping away the last of their time together like the bottle of wine in the cooler. The rest could come later.


End file.
